Pure anti-dsDNA mAbs need chromatin structures to promote glomerular mesangial deposits in BALB/c mice

The glomerular targets for nephritogenic antibodies have been identified as membrane-associated chromatin fragments. The processes responsible for their deposition are poorly understood. To determine early events in antibody-mediated nephritis, we injected highly pure anti-dsDNA mAbs into BALB/c mice. Mice receiving one dose of anti-dsDNA mAbs were sacrificed 6 or 24 h later. No direct binding of mAbs to glomerular membranes or to the mesangial matrix was observed by immune electron microscopy. In contrast, repeated injections of the same antibodies over 4 weeks resulted in deposition of electron dense structures predominantly in the mesangial matrix. These structures contained mAbs and chromatin fragments as determined by co-localization immune electron microscopy. Biotinylated anti-dsDNA mAbs, injected into nephritic (NZB x NZW)F1 or MRL